1. Field of the Invention
The present invention relates to a medical implantable lead of the kind being adapted to be implanted into a human or animal body for monitoring and/or controlling of an organ inside the body, having a penetrating fixation element in a distal end, which is adapted to penetrate into the tissue of the organ to fixate the lead such that a distal end of the lead will be in contact with the organ, an electrode member to receive and/or transmit electrical signals from and/or to the organ, and an indication arrangement of a radiopaque material for visibility by means of fluoroscopy in an implanted state.
The invention also relates to a method for ensuring proper and safe attachment of a medical implantable lead to an organ inside a human or animal body.
2. Description of the Prior Art
Within the area of medical implantable leads, it is common practice to use a penetrating fixation element to fixate the lead to an organ to be monitored and/or controlled, i.e. the lead is fixated to the organ by means of a fixation element which is penetrated into the organ for engaging the tissue and maintain the lead in electrical contact with the organ. Normally, the fixation element has the form of a helix, which is screwed into the tissue, but also other types of penetrating fixation element can be conceivable, such as straight and sharp fixation element having barbs and the like. Moreover, the penetrating fixation element may also function as an electrode, which is to be embedded into tissue and receive and/or transmit electrical signals from and to the tissue, respectively.
When fixating a medical implantable lead to an organ by means of a penetrating fixation element, it is important that the penetrating fixation element is completely embedded into tissue. This is important for the mechanical stability, in order to permit the lead to be maintained fixated to the organ during a long period of time. This is also important for the electrical performance, in the case of the penetrating fixation element itself being an electrode, or if an electrode surface on the distal end of the lead is to be held in close contact with the tissue. Moreover, if the penetrating fixation element functions as an electrode, the impedance of the electrode will be reduced in case the electrode is not completely embedded into tissue but instead the electrode is at least partly in contact with e.g. free blood or other body fluids. Reduced impedance will increase the energy consumption when transmitting signals between the organ and a monitoring and/or controlling device, which normally is battery operated.
If the penetrating fixation element is a helix, which is screwed into the tissue, there is a risk that the physician performing the attachment may apply too much torque to the helix in order to be sure that the helix is completely embedded into the tissue. This may cause damage to the tissue in form of tearing or perforation of the tissue if the organ has a comparatively thin wall, such as is the case with e.g. a heart.
In prior art, medical implantable leads are known having a penetrating fixation element in form of a helix, which is rotatable in relation to the lead and at the same time extendable out from a cavity in a so called header sleeve in the distal end of the lead. In order for the physician performing the attachment to see when the helix is completely extended from the header sleeve, an indication arrangement of a radiopaque material is provided which can be seen by means of fluoroscopy during implantation. The indication arrangement has a fixed indication marker positioned on the header, e.g. shaped as a ring, and a movable indication marker positioned on or forming the helix or a shaft on which the helix is mounted. During implantation, the physician can see the fixed and the movable indication markers by fluoroscopy, and when a predetermined number of helix coils is visible beyond the fixed indication marker or they assume a predetermined position in relation to each other, e.g. coincident with or close to each other, the physician can be sure that the helix is completely extended from the header sleeve. However, this does not necessarily imply that the helix also is completely embedded into tissue.